Provided is a compound showing excellent Antifungal activity against Trichophyton fungus, which is a major causative microorganism of superficial mycosis, and high effectiveness on diseases caused by Trichophyton fungi. A biaryl derivative represented by the formula (I) or a salt thereof: wherein ring A is an optionally substituted phenyl, or an optionally substituted 5- or 6-membered ring heteroaryl (ring A may be further condensed to form an optionally substituted fused ring); Q is CH2, C═O, NH, O, S or the like; X1, X2 and X3 are CR1 or N; Y is CH or N; Z is CR2b or N; R2a and R2b are each a hydrogen atom, a halogen atom, an optionally substituted C1-C6 alkyl group, a C1-C6 haloalkyl group or the like; R2a and R2b may form, together with carbon atoms bonded thereto, an optionally substituted carbocycle, or an optionally substituted heterocycle.